A multicolor paint is a paint which, when coated on a surface and dried, results in a coating that is characterized by dispersed discrete spots (or dots). Water-in-water multicolor paints have heretofore been proposed (see, for example, Sellars et al. U.S. Pat. No. 3,950,283, Grasko U.S. Pat. No. 3,852,076 and Zola U.S. Pat. No. 4,376,654) and are of commercial interest particularly in view of the developing governmental interest in establishing regulations limiting the quantity of organic volatiles emitted into the surrounding environment by a paint during application and subsequent air drying. The state of California, for example, is reportedly considering the adoption of regulations limiting such paint emissions.
It is difficult to prepare a commercially acceptable water-in-water multicolor paint because of various problems. One problem is the fact that the discrete color bodies comprising the disperse phase in such a paint need to contain a relatively high concentration of a water soluble, film-forming polymer in order to achieve commercially acceptable characteristics in a coating made therewith. Another problem is that such polymers should be in a highly water insoluble state after the paint has been coated and dried; otherwise, the coated and dried paint provides little or no water resistance. Another problem is to prepare and utilize a disperse phase composition which can be formed into discrete color bodies that have sufficient structural integrity in the continuous phase of the paint for practical commercial purposes. Structurally weak discrete color bodies would break up easily and become part of this continuous phase.
Prior art multicolor paints commonly contain a solution or dispersion of a film-forming polymer in an organic liquid carrier with such polymer being, for example, nitrocellulose or styrene butadiene, and such carrier liquid being mineral spirits or the like. However, the solubility and dispersibility of such polymers in water is so small as to make it impossible to use such polymers in making a water-based paint of commercially acceptable quality. It is also not practical to "fortify" the water with a water-miscible organic co-solvent to enhance polymer solubility or dispersibility because the maximum amount of the organic co-solvent which can be present should be kept below about 3 weight percent on a total product paint composition basis in order to comply with the foregoing proposed regulatory standards.
So far as now known, no one has previously succeeded in preparing a water-in-water multicolor paint wherein the aqueous disperse phase color bodies are characterized by having:
(a) a relatively high content of water soluble film-forming crosslinkable polymer in association with a crosslinking agent, PA1 (b) a relatively high structural integrity, and PA1 (c) a capacity to form highly crosslinked water insoluble coatings after paint application and drying. PA1 (a) water dispersable, film-forming, cross-linkable, carboxylated polymer, and PA1 (b) hydroxy (lower alkyl) cellulose and/or alkali metal carboxyl (lower alkyl) cellulose.